A main drawback for currently applied engineering modeling is that large models in the industry with so many unorganized inside and outside relations are hard to survey and understand by engineers at definition of new contributions. The authors developed a new concept and methodology to improve current product modeling by an extension to new content based model entities. Content is defined by human and processed as background knowledge of decisions on engineering objects. A significant question is how knowledge can be represented in this extended product model. In this paper issues in the answer are dicussed. Product model is introduced considering its application in industrial product lifecycle management (PLM) systems. As a basic idea of the proposed modeling, contextual definitions for engineering objects are explained. Current modeling is defined as classical one and is compared with the proposed way of product definition. Knowledge based issues are discussed such as process and representation in the proposed global modeling, product and knowledge object levels in models, relating parameters of engineering objects. Finally, critical role of consistency and context definitions in product models are emphasized.